Means for and methods of using a selected energy factor to apply a paper coating

ABSTRACT

A continuous output system makes paper coating by combining an emulsifier with ASA particles having a mean average size in the low to sub-micron region. A turbine, pump, blender or other device exposes the ASA to a number of repeated episodes of high shear until the resulting ASA is in the form of particles having a mean average diameter in approximately the 1μ range. The measure of the amount of high shear is identified by an energy factor index. A system for cooling the ASA enables the processing without causing a hydrolyzing of the ASA, even when a heated cooked emulsion is used.

This application is a continuation of application Ser. No. 09/755,239,filed Jan. 5, 2001, which is a continuation-in-part of application Ser.No. 09/136,677, filed Aug. 19, 1998, now U.S. Pat. No. 6,207,719.

This invention relates to means for and methods of using a selectedenergy factor to apply an ASA sizing or coating to paper and moreparticularly a system having means for preventing a build-up of ASA oninside surfaces of apparatus that is used to produce the sizing.

Reference is made to my U.S. Pat. No. 5,653,915 for more information onASA coating systems. As good as it is, this system, like most papercoating systems, suffers from a build-up of ASA on inside surfaces ofpipes, nozzles, valves, and other parts of the system. The build-upgenerally required a periodic back flushing and clean out every 2-4months. With the invention, the time between this periodic back flushingcan be extended many fold.

This build-up occurs because, when it is added to pulp stock during apaper making process, a hydrocarbon based ASA polymer material forms aprotective barrier, resists moisture intrusion into the paper, andprovides a conditioned surface for the application of inks to paper.Those same characteristics tend to form a similar barrier on the insidesurfaces of the system pipes, vales, nozzles, etc.

Accordingly, a desired feature of the invention is to reduce the area ofthe inside surface, and in particular, to eliminate minute spaces wherethe build-up quickly forms and decreases the quality of the emulsionproduced by the system. One such minute space is the atomizing nozzlewhich reduces the ASA to a spray of fine particles which may be thoughtof as tiny droplets of oil suspended in a liquid, such as water, forexample. Heretofore, these particles have been formed by atomization,but the atomizer nozzles have tended to be clogged by the ASA. Anotherconcern is the large amount of internal surface area presented by theplurality of inter-connecting pipings in contact with the ASA emulsionduring the processing.

The quality of the ASA coating is largely dependent on the particle sizeof the colloidal droplets. Particle counters, particle size analyzers,and microscopes are available to estimate the particle size. While thesetools are effective, they are also tedious and more importantly,intermittent, so that traditionally there has been no continuousmonitoring of particle size during the production thereof. Therefore,samples had to be drawn from an emulsification unit and analyzed in alaboratory in order to determine particle size. With such anintermittent testing, any changes in the quality of the emulsion on-linewould not be detected in time to prevent at least some poor sizingperformance on the paper machines. My U.S. Pat. No. 5,730,937 describesa monitor and sensor which is able to continuously monitor a flowingstream for particle size and concentration, and to send control signalsin response thereto.

ASA emulsions are stabilized either by cationic starches (a naturalpolymer) or by proprietary synthetic polymers or starch/polymers. Papermills have their own and proprietary process and method of treatingpaper. As part of their process, the paper mill may elect to use eithera cooked starch or a combination of starch and polymer as an emulsifier.The cooked starch is about 4% solids and is introduced into theprocessing system at a temperature in the nature of 100° F. Cookedstarch does not have to be diluted with water, but it needs to be cooledto prevent a deterioration of the ASA. The combined starch/polymer is inthe range of about 25-35% solids, but it is at a lower and usuallyambient temperature. It does need to be diluted with water to reduce theratio of solids to liquids, but it does not have to be cooled.

From the viewpoint of someone practicing this invention, the customerusually prescribes not only the surfactant to use along with anidentification of the polymer to be processed, but also supplies aliquid with the surfactant already in the ASA. Regardless of whether acationic starch or a synthetic polymer is used, an additional surfactanthas been required in the emulsification step. The surfactant provides aboundary layer resistance to shear for the ASA particles. Thissurfactant is normally a non-ionic alkyl phenol ethoxylate. Thecomposition of most surfactants is a trade secret which is closely heldby the manufacturer, causing an increased uncertainty which makes thedesign of a general purpose system more difficult.

Since the user of my system must accept and process the prescribedblends, it must be versatile enough to work with virtually all blends.Accordingly, an important virtue of the inventive system is that it isso versatile that it may be used with almost all of the proprietarypaper making process by making only slight modifications to the system.

Putting these thoughts together, a system has to impart enough energy toa blend of ASA emulsifier and surfactant to break it into very fineparticles. My above identified patent supplies the energy by acombination of a nozzle, subject to clogging, and a high pressure pump.To eliminate the nozzle, another form of device must be provided toimpart the energy. If, in the process of imparting such energy, asubstantial cost savings can be realized, the system is even better.Since the nozzle and high pressure pump were among the more costly partsof my earlier system, improvements of the described type are highlydesired.

In keeping with an aspect of the invention, the system uses any ofvarious mechanically means to break-up the blend of ASA and surfactantinto fine particles. These means involve devices such as turbines,blender and the like. The invention solves the problem of reducing theinternal surface area of the system by drilling holes in a block ofmetal so that the bores of the holes perform the finctions of a networkof pipes. The longest of those bores is only a few inches. I havereduced the costs of the system by a factor of 40-50% as compared to thecost of prior art systems. Also, I have formed ways of making systemshaving a capacity in a range from very small to very large with only asmall amount of system modification.

The term particle “size” refers to the average mean diameter/volume ofthe particles. Of course, the actual size of the particles will bedistributed in a manner described by the well known Guassian orbell-shaped curve. Therefore, some particles will be larger and somesmaller than the average cited in this specification.

The success of the sizing is directly related to the quality of theemulsion (ASA particle size). If the ASA colloidal particle size is notsmall enough, there is a less stable emulsion and a lower retention ofthe size. In general, the smaller the particles, the better, a usefulaverage mean diameter range being about 0.1-3.0 microns, with a range ofabout 0.5-1.5 m preferred. A high level of size retention is mandatoryin any ASA sizing system which means less re-circulation of ASA in awhite water system and fewer problems associated with hydrolyzed ASAwhich occurs when ASA chemically reacts with water and which forms agum-like particle called a “stickie”. The conflict for the systemdesigner is to make the particles as small as possible without degradingthe molecules of the starch and causing the ASA to react with water. Oneof the reasons why smaller particle size is so important is that it doesless damage to paper making machine which tend to gum up, if theparticle size is too large.

Because the internal phase is made up of the ASA, the emulsion isclassified as an oil in water (“O/W”) emulsion. The two most commonnatural polymer emulsifiers (external phase) are corn and potato starchwhich are chemically modified to enhance their cationic chargecharacteristics. Another approach utilizes synthetic polymers in lieu ofstarch. The starch or polymer surrounds and protects the ASA thusencapsulating the ASA to keep it from hydrolyzing. In effect, the starchis the protective barrier for the particles of oil (ASA) to be spread onthe paper. The “oil” is an internal coating which makes the paper waterresistant and receptive to ink.

One consideration which goes into the design of my system involves acalculation of how much energy is required to produce the ASA particleshaving a desired particle size. In an exemplary mill application, theASA and starch (or other suitable emulsifier) are metered through anemulsification unit designed to impart energy to the mixture to create asuitable and stable emulsion. The emulsion is then metered onto thepaper. There the ASA emulsion combines with the furnish.

I have found that I can produce superior results with a mixing headcosting under $1,000 and using standard commercial items, such as thoseshown in FIGS. 5-10. For example, a turbine that is useful with theinvention may be almost any of those manufactured by MTH PUMPS of 401West Main Street, Plano, Ill. 60545, although one of their turbines, maybe preferred over other of their turbines for any given installation. Tothis mixing head, there must also be added the cost of controls,sensors, and the like. However, the cost for controlling these standardcommercial products is generally less than the controls which must bedesigned for special equipment. I have found that in order to achieve aproper particle size with a good distribution, two things should happen.First, a proper number of shearing events should occur in an order ofmagnitude of at least about 150,000 shear events per minute. Second, theblade tip speed should be at least about 5000 feet per minute.

In order to quantify the number of shearing events for the emulsion,reference may be had to the following equations: $\begin{matrix}\frac{\begin{matrix}\text{(Number~~of~~Shearing~~Events/Minute)} \\\text{(Velocity~~of~~Blade~~Tip~~Ft/Min)} \\\text{(Duration~~of~~Contact~~Time~~in~~Minutes)}\end{matrix}}{1,000,000} & (1)\end{matrix}$

From the information published for various standard commerciallyavailable machines and by using Equation 1, the following table can becalculated: TABLE 1 ENERGY FACTOR Standard Centrifugal Pump 79 StandardTurbine Pump 361 Laboratory Blender 752 High Speed Centrifugal 138 HighSpeed Turbine 1020 High Speed Stack Centrifugal Pump 620

The “Energy Factor” is a dimensionless index which gives an indicationof the efficiency of the various mixing machines. Table 1 shows that thestandard centrifugal pump, the standard turbine pump, and the high speedcentrifugal pump are not very good. The remainder of these mixingmachines have an “energy factor” index in the range of 620-1020 whichmakes them acceptable. Depending on the choice of blade or impellerdesign and on the fixed rotational speed, the variable that comes intoplay is the duration of the contact time between the blade and the ASA.The maximum contact should not exceed 3 minutes. Any number below thisthree minute value is acceptable if it satisfies the required particlesize. However, for most uses, with one exception, the optimal time hasbeen found to be approximately one minute of contact time. The onlyexception found to date is the laboratory blender. Due to itscombination of small blades and high rotational speed, about twentyseconds is usually adequate. If the duration of the contact time in theblender is in excess of one minute, there can be a latent heat buildupin the emulsion.

In greater detail, tests have shown a continuous improvement of ASA witha reduction of particle sizes. These tests have gone down to particlesize having a diameter as small as about a quarter of a micron. Hence,the finer the particles, the better the reaction with the paper fibers.However, if the imparting of energy goes on too long, hydrolyzing mayoccur where there is a chemical reaction between the ASA and water. Inthis chemical reaction, heat acts as a catalyst. Therefore, there is arace against time between making particles as small as possible and theaccumulation of enough heat to cause hydrolyzing.

The distribution and mean particle size of an exemplary ASA emulsion maybe analyzed by a Honeywell particle size analyzer using laser refractionalgorithms. The Microtrac (Honeywell) analyzer presently costsapproximately $50,000, is calibrated to NIST standards, and isrepresentative of particle size analyzers now used in the paper industryin order to track ASA performance. In this example of a particle sizeanalysis, an ASA particle size (9.543 mv) is too large to be useful as asizing agent. By increasing the energy value applied to the ASA, themean particle size drops to about 1.355 mv, for example. Although theparticle is smaller, the distribution (smallest to largest) is still toowide. The same ASA material may be brought into a suitable range with anadditional fine tuning adjustments of the emulsifier (energy factor andcontact time). While the mean particle size has remained virtually thesame, the distribution of particle sizes has significantly narrowed witha much more desirable profile with respect to sizing performance on thepaper machine.

To make smaller particles, the invention in general depends upon animparted energy factor which, in turn, depends upon a number ofdifferent parameters: the number of blades on an impeller, number ofimpellers, revolutions per minute, and duration of the exposure of ASAto the shearing events. Any one or more of these factors may be variedso that there is a trade-off between the parameters. The limiting factoron the upper end of an imparting of high energy is the heat generated bythe impeller operation. If the energization of the fluid makes it toohot, the ASA becomes unstable. Also, the heat may degrade the starch orother emulsifier.

This suggests that parameters other than the impeller and rotations perminutes may also play important roles in the preparation of ASA. Forexample, the ASA, water, and emulsifier may be introduced into thesystem at, say 33° F. or 120° F., or any other temperature. (Obviously,more shearing events, or energy input, may occur when the inflowingstreams are cold than when they are hot). Also, the entire system orparts thereof may be cooled to enable an imparting of more shearingevents especially when the inflowing liquids are hot. For example, tocool the processed fluids, the entire system may be housed in atemperature controlled environment, such as a cooling housing; or, therecycle loop may be run through a heat exchanger such as a plate andframe heat exchanger, a tube heat exchanger, a heat sink having coolingfins, a radiator, or a combination thereof.

Another way of controlling the heat is to control the volume of fluidsintroduced into the processing system. For example, in a supersimplistic way, a gallon of water energized for one minute mightaccumulate twice as much heat as two gallons of water energized for oneminute.

A moment of thought will suggest many other ways of controlling theamount of heat build-up in the processing system as energy is impartedto the ASA.

Using a preferred range of one minute of contact time, we can comparethe prior art to the invention, as follows:

PRIOR ART

Standard turbine with a 29-blade, four inch impeller, turning at 3450RPM. To calculate the blade tip velocity (V) in Ft/Min $\begin{matrix}{V = \frac{2\pi\quad{r({RPM})}}{12}} & (2)\end{matrix}$where r=radius of impeller$V = {\frac{2(3.14)(2)(3450)}{12} = {3611\quad\text{ft/min}}}$

To calculate shear events/min:(Number of blades)×(number of impellers)×(Rev. per minute)29×1×3450=100,050  (3)

To determine the energy factor: $\begin{matrix}{\frac{\begin{matrix}{\left( {{Shearing}\quad{{events}/\min}} \right)(V)} \\\left( {{duration}\quad{of}\quad{contact}\quad{in}\quad\min} \right)\end{matrix}}{1,000,000}{\frac{(100050)(3611)(1)}{1000000} = 361}} & (4)\end{matrix}$

According to the teaching of the invention over the prior art, we nowsee that: High speed turbine at 5800 RPM with a 29-bladed impeller of 4″diameter $V = {\frac{2(314)(2)(5800)}{12} = 6070}$

Shear events/Min(Number of blades)(number of impellers)(Revs per minute)(29)(1)(5800)=168200 shear events/min  (5)

Energy Factor $\begin{matrix}\frac{\begin{matrix}{\left( {{Shearing}\quad{{Events}/{Min}}} \right)(V)} \\\left( {{Duration}\quad{of}\quad{Contact}\quad{in}\quad{Minutes}} \right)\end{matrix}}{1,000,000} & (6)\end{matrix}$

This example shows that the energy factor has increased (361 vs. 1021)substantially over the prior art for the same duration of the emulsioncontact time. This 2.8 times increase $\frac{1021}{361} = 2.8$

Improves the efficiency of the emulsification unit, resulting inimproved particle size and distribution.

Calculations

To calculate blade tip velocity $\begin{matrix}{V = \frac{2\pi\quad r \times {RPM}}{12}} & (7)\end{matrix}$where:

r=radius of shearing blade or impeller in inches

RPM=speed of blade in revolutions/minute

V=Velocity expressed as ft/minute

To calculate shearing events/minuteB×N×RPM=SPM  (8)where:

B=number of blades

N=number of stacks or impellers

RPM=revolutions/min

SPM=shearing events/min

To calculate shearing factorV(t)=SFwhere:

t=time of exposure to shearing blades in minutes

V=shearing velocity

Examples of shearing factor

High Speed Turbine

Diameter of impeller=4 inches

Number of blades=29

Number of stacks=1

RPM=5800

Duration of Exposure time=1 min.

From Equation (7): $V = {\frac{2{{\pi 2}(5800)}}{12} = 6070}$

V=6070

SF−6070×1=6070

High Speed Blender

Diameter of impeller=2 inches

Number of blades=4

Number of stacks=1

RPM=33,000

Duration of Exposure Time in Minutes=0.66 min

(From Equation (7))$V = {\frac{2\pi\quad{{r1}\left( {33,000} \right)}}{12} = 17270}$

V=17270

SF=17270×0.33=5699

High Speed Centrifugal

Diameter of impeller=5 inches

Number of blades=5

Number of stacks=1

RPM=4600

Duration of Exposure Time=1 min

From Equation (7) $V = {\frac{2{\pi 2}{.5}(4600)}{12} = 6018}$

Using “29” blades with (3) minutes of contact, the energy factorbecomes:(29) No. of blades×(1) No. of impellers×(5800) rpm=168,200 shearevents/min $\frac{\begin{matrix}{\left( {168\text{,}200} \right)\quad{shear}\quad{events}\text{/}\min \times} \\{(6070)\quad{velocity}\quad{ft}\text{/}\min \times} \\{(3)\quad{contact}\quad{in}\quad{minutes}}\end{matrix}}{1\text{,}000\text{,}000} = {3063/{factor}}$

This represents a threefold increase over the original example of a1020/factor using 1 minute of contact time. However, the target energyfactor is 5623 based on the actual contact time and the number ofturbine blades on he MTH pump. Since the MTH pump has blades on eachside, there is a doubling of the number of blades due to their staggeredarrangement on opposite sides of the turbine. This makes the number ofblades jump from 29 to 58, giving the following results:(58) No. of blades×(1) No. of impellers×(5800) rpm=336,400 shearevents/min$\frac{\begin{matrix}{\left( {336\text{,}300} \right)\quad{shear}\quad{events}\text{/}\min \times} \\{(6070)\quad{velocity}\quad{ft}\text{/}\min \times} \\{(3)\quad{contact}\quad{in}\quad{minutes}}\end{matrix}}{1\text{,}000\text{,}000} = {6\text{,}{126/{factor}}\quad{for}\quad{three}\quad{minutes}}$

Calculation for 160-Blade Turbine

Shear events per minute:(Number of Blades 160)(Number of impellers 1)(Revs per Minute 5800)(160)(1)(5800)=928,000 shear events per minute

In the next step, calculating the energy factor, substituting 928,000SPM for 168,200 SPM in Equation 5 yields:(Shear Events/Min 928,000)(V6070)(Duration of Contact in Minutes 1)$\begin{matrix}{\frac{\left( {928\text{,}000} \right)(6070)(1)}{1\text{,}000\text{,}000} = 5632} & {{Energy}\quad{Factor}}\end{matrix}$

However, for eample of 160 blades (blade count on the MTH turbineactually used), the energy factor for 3 minutes would be calculatedthus:(160 No. blades×(1) No. of impellers×(5800) rpm=928,000 shear events/min

$\frac{\begin{matrix}{\left( {928\text{,}000} \right)\quad{shear}\quad{events} \times} \\{(6070)\quad{velocity}\quad{ft}\text{/}\min \times} \\{(3)\quad{contact}\quad{in}\quad{minutes}}\end{matrix}}{1\text{,}000\text{,}000} = {16\text{,}{899/{factor}}}$TABLE 2 Duration in Minutes RPM Blade Tip Speed Of Contact Time 3450Centrifugal 4513 1 3450 Turbine 3611 1 33,000   Blender 17270 0.33 4600H.S. Centrifugal 6018 1 5800 High Speed Turbine 6070 1

When the mechanism of particle size retention is not fully understood,it is thought that once established, a very small particle size tends toform a better distribution in the emulsion. However, it also seems that,after the small particles are formed, and if they do not have time tostabilize some of them may attract each other so that they come togetheragain, thus clumping and reforming into big particles. These biggerparticles can adversely affect the mechanical properties of the coating.

BRIEF DESCRIPTION OF DRAWINGS

A preferred embodiment of the invention is shown in the attacheddrawings, in which:

FIG. 1 is a block diagram of my relatively simple prior art system foractivating or inverting polymer;

FIG. 2 is a manifold block for use in the system of FIG. 1;

FIGS. 3-4 are two views of a static mixer comprising an end view, and aside elevation;

FIG. 5 is a plan view showing the front of a turbine for impartingenergy to the ASA;

FIG. 6 is a schematic view of a pump impeller for imparting energy tothe ASA;

FIG. 7 is a schematic view of a vertical stack centrifugal pump;

FIG. 8 is a schematic view of a blender for imparting energy to the ASA;and

FIGS. 9 and 10 are two schematic views showing ways of modifying bladesfor increasing the opportunity for ASA to encounter shear events;

FIG. 11 is a schematic diagram of the inventive system;

FIGS. 12-15 are four views of an inventive manifold block for replacingthe ASA/polymer transportation and delivery system of FIG. 11, FIG. 12being a top plan view, FIG. 13 being at left, elevation view, FIG. 14being a front elevation view, and FIG. 15 being a right end elevationview;

FIG. 16 is a fragment of FIG. 11 showing an important part of the systemin a temperature controlled enclosure to prevent or control heatbuild-up during the energization of the ASA;

FIG. 17 is another fragment of FIG. 11 also showing an important part ofthe system using a heat exchanger in the recycle loop;

FIG. 18 is a modified copy of FIG. 11 which provides details of detailsof a heat exchanger used to cool cooked starch and the recycledASA/Emulsion blend being processed; and

FIG. 19 is another modification of FIG. 11 showing an embodiment whichreduces the need for expensive control valves.

An early form of a mixing manifold is shown in FIGS. 1-4 taken from myU.S. Pat. No. 5,372,421, which use the conventional network of pipesforming the delivery and transport system which conveys the ASA. Theinvention uses a mixing manifold block to reduce the inside surface areaof the network of pipes.

In FIG. 1, the polymer inverting and activating system components are acentrifugal pump 20 for introducing water, a closed mixing loop 22,mixing manifold 24, and a centrifugal pump 26 for introducing thepolymer in to the manifold. The water and polymer first meet in themixing manifold 24, the water flow being indicated in FIG. 1 by solidlines and the polymer flow being indicated by dashed lines.

In greater detail, the mixing manifold 24 (FIG. 2) is, for example, asolid block of metal having a central bore 28 extending throughsubstantially its entire length. The bore stops short of counter boredand threaded input opening 30, to form a bulkhead 32. An orifice 34 of aselected diameter is formed in the center of the bulkhead 32 toestablish communication between the water inlet hole 30 and the centralbore 28, with a flow rate that is controlled by the orifice diameter.The polymer solution experiences an extrusion type of shear as it passesthrough the orifice 34.

A first threaded hole 36 leads to another bulk head 38 between theentrance to the counter bored and hole 36, and the central bore 28. Anorifice 40 is formed in the bulkhead 38 to establish communication andto control the flow rate between the hole 36 and the central bore 28.

The output port 42 is in direct communication with the central bore 28to give an unimpeded outflow comprising a mixture of polymer and water.

A static mixer 46 (FIGS. 3 & 4) comprises two sets of semi-ellipticalbaffles which are set at an angle with respect to each other so that theoverall end view configuration is a circle (FIG. 3) which corresponds tothe inside diameter of the central bore 28. Therefore, the static mixer46 slides through an end opening 51 and into the bore 28. The baffles 48on one side of the static mixer are a series of spaced parallel plates.The baffles 50 on the other side of the static mixer are joined onalternate ends to give an overall zigzag appearance. A plug 52 seals offthe end of the bore. A gauge shown at 54 fits into a hole 56 that is incommunication with bore 28.

An inspection of my ASA U.S. Pat. No. 5,653,915 reveals a manifoldhaving a nozzle at the ASA inlet. This is the relatively expensiveatomizing nozzle which, like most nozzles for ASA, is subject toclogging after a relatively short period of use. An elimination of thisnozzle simplifies the system, reduces the cost thereof, and eliminates asource of relatively early clogging. However, before eliminating thenozzle, some other means is required for imparting enough energy tobreak the ASA into tiny particles. For a description of such means forimparting energy, reference may be made to FIGS. 5-10, as examples ofvarious means for reducing ASA to the particle size.

FIG. 5 shows the front of a turbine 60 having a multi-blade rotor 62turning about a shaft 64 in a housing 70. The ASA passes from one sideof the turbine through the blades and out the other side. The collisionsbetween the ASA and the blades are the shear events which form theparticles. There is an extremely small clearance 66 between the tips 68of the turbine blades and the surrounding housing 70 so that very littleof the ASA which has passed through the blades feeds back to the inputside of the turbine.

FIG. 6 schematically shows a pump 72 having an impeller 74 mounted torotate within a housing 76. The ASA material which is to be broken intoparticles falls into an eye 78 of the impeller from which it is flungout by centrifugal force. All of the ASA will be struck by the blades80. Much of the ASA will strike the housing 76. A good portion of theASA will feed back into the blades and be struck repeatedly. Each ofthese encounters imparts some shear and breaks the particle in order toreduce their size. A portion of the ASA will leave the housing at 82.

FIG. 7 schematically shows a stack 84 of centrifugal impellers which areenclosed with in a common housing 86, which are mounted to turn on acommon shaft. The housing has an inlet 88 and an outlet 90 for ASA toenter, at 92 and leave at 94. Inside the housing, there are any suitablenumber of impellers 96-100 mounted to turn as a unit. Each impeller hasa scroll plate 102 which turns with its individually associated blade104.

As the ASA 92 enters the housing inlet at 88, it encounters and passesthrough an eye 106 in the scroll plate 102. The rotation of the impellercauses the ASA to emerge from stage 96 with a certain pressure. Thedesign of the successive impeller stages 96, 98 . . . 100 is such thatthe pressure at the eye of the next successive eye (such as 108) sucksthe ASA from the preceding stage. Thus, the ASA 92 enters eye 106 on thescroll plate 102 of stage 96, passes through the impeller blades 104 andis sucked into eye 108 on the scroll plate of the next succeeding stage98.

In a similar manner, the ASA passes from stage to stage until it reachesthe last stage 100 where the centrifugal force of the impeller flingsthe processed ASA 94 out the exit 90.

FIG. 8 schematically shows a blender 110 having a container 112 forreceiving the ASA. In the bottom of the container, a number of blades114 are mounted for rotary motion, driven from a motor in the base 116.

I have found that blenders work very well, although not as well asturbines. A blender, for example, has almost nothing to separate thematerial that has and the material that has not experienced shear.

Stated another way, a turbine with only a very little feedback whichproduces, say, 10,000 opportunities for shear during a given time periodis not completely matched by a blender which produces the same 10,000opportunities. However, the blender produces particles that are almostas good as the particles produced by a turbine. The “energy factor”index (752) for a blender may be better than the index for some highspeed turbines with small clearance and little feedback; however, thereis as much reason to believe that this may be due to the many turbineblades as it is to believe that it is due to the small clearance. Henceit is clear that the number of shearing events is more important thanthe prevention of feedback or the other factors thought to be importantby the prior art. Because it has mechanical limitation, the blender isbest when limited to a use within a laboratory environment. There aretrade-offs considering the low cost of the blender, the size of thesystem and a possibly short life time of the blender.

FIGS. 9 and 10 are examples of how the blades of any of these devicesmay be modified to create more shear events without increasing eitherthe speed of rotation or the number of blades. For example, in FIG. 9,the blade 118 has a notch 120 cut into it so that, if rotating indirection A, the number of sharp edges (122-128) striking the ASA hasbeen doubled over the number of edges on a blade without a notch. InFIG. 10, the blade 130 has three pegs 132, 134, 136 projecting from eachside. As the blade rotates, each of these pegs strikes the ASA to addshearing events. Of course, these two examples are given merely toillustrate a principle. Many different modifications of the blades arepossible.

The inventive system is schematically shown in FIG. 11 which uses theprinciples described above. The principal parts are a manifold 200, aturbine 202, a source of ASA 204, a source of polymer 206 (either starchor synthetic), flow meters 208, gear pumps 210, 212, throttle valves, as214, 216, 218, pressure controllers 220, 222, flow controllers, 224,226, check valves 228, 230, an EPIC sensor and monitor system 232, and acontrol panel 234 including a programmable logic controller (“PLC”)micro-processor 236. Pressure gauges are shown at 238, 240.

The inventive system (FIG. 11) has a suitable tank 204 which stores theASA, usually pre-blended with a surfactant in the range of 0.5-4% byweight of the total blend. If desired, the tank 204 may include onlyASA, while the surfactant is separately introduced at 242. A suitablegear pump 210 delivers the mixture through a suitable strainer, such asa 100-mesh strainer. Pump 210 provides a positive head in the range of10-60 psi, which flows through check valve 228 to input 242 on manifold200. A pressure gauge 240 gives a continuous reading of the ASA pressurein the manifold 200.

The speed of pump 210 is controlled by the programmable logic circuit236, preferably in the form of a micro-processor, via a variable speedterminal 243. The output of pump 210 may be in the range of 100-200 psiwith 40-60 psi preferred. A check valve 228 passes the ASA in thedirection of the arrow (i.e. toward the manifold 200 ) and prevents aback flow from the starch/polymer line which would contaminate thepristine ASA mixture.

The starch/polymer is transmitted under the pressure of pump 212 fromany suitable source 206 via a line 246 and check valve 230 to manifoldinput 248. The starch/polymer pump 212 delivers the starch/polymer at arate in the order of 0-10 gpm, for most systems. Obviously, a differentvolume may be used in other systems.

An electrolyte, herein a form of water, is introduced into the manifoldvia throttle valve 214 and flow meters 208, a primary dilution waterpath may be traced through throttle valve 216, and flow regulator 224 tomanifold inlet 250. This primary dilution brings the ASA andstarch/polymer to a desired consistency. A secondary dilutionelectrolyte path is traced through flow meter 254, throttle valve 218,flow regulator 226 and check valve 256 to the output 258. The secondarydilution path provides enough water to fine tune and brings the finaloutput to a desired consistency.

As here shown, turbine 202 includes a motor 260 coupled through a shaft262 to a turbine 264 constructed somewhat as shown in FIG. 5. Dependingupon the needs of the system, any of the devices of FIGS. 5-10 may beused; a pump made by the MTH Company of Piano, Ill. is preferred. TheASA/polymer/water mixture enters the manifold 200 at entrance 203. Theturbine 264 imparts enough energy to break the ASA into tiny particlesof a desired size with a recycle out flow over a path 266 shown by adot-dashed line. Recycle is controlled by flow regulator 222. Therecycle out flow divides, part going back into the manifold 200 atentrance 268 and part entering manifold 200 at entrance 270.

A relatively small percentage of the mixture exits the manifold 200 atoutlet 272 and travels through flow regulator 220 and sensor 232 to thesystem output at 258.

Control means are provided for enabling a continuous testing ofparticles during a production run. Primarily, the prior art usednon-continuous sampling as their only available means to verify thequality of the emulsion. At monitor and sensor 232, the inventive systemprovides the EPIC (Enhanced Polymer Imaging Controller) of U.S. Pat. No.5,323,017 to continuously monitor the quality of the emulsion. Briefly,this patent discloses a source 233 of preferably laser light shiningthrough a flowing output stream of an ASA emulsion. The light fromsource 233 is sensed at 231 and a signal is sent to control panel 234 inresponse thereto. Hence, the EPIC controller uses a laser supplied lightto apply a combination of light scatter and absorption principles toestablish a spatial distribution of ASA and polymer composites whichaccurately corresponds to particle size and particle concentration. Thissensor detects instantaneous changes in the ASA particle sizeconcentration, which can be used to control the system and can bedisplayed (not shown) at a main control panel 234. This sensor ismanufactured by Norchem Industries of Tinley Park, Ill.

Because the sensor 232 scans the emulsion with coherent (laser) lightand monitors only selective wavelength it can be fine tuned to look forparticles within a specific refractive index in an extremely narrowbandwidth (5-20) nm). Also, because the refractive index of a substancewhich is varied for different wavelengths, conventional light scatteringinstruments are not always as reliable. Unlike turbidity meters ornephelometers which use a white light from a thermal radiation source,the laser eliminates all refractive index differences for all thewavelengths except those emanating from the source. All that remains toaffect the light scatter, is the particle size, shape (distribution),and concentration.

One of the problems is that the buyer of the inventive system does notknow in advance exactly what component material will be processed duringthe lifetime of the system. For example, the starch/polymer may be madefrom any of many different raw material. There are a number of differentASA's with a great variety of molecular weights or other wide variances.There are thought to be thousands of different surfactants, each withits own particular characteristics. The EPIC controllers helps toovercome the resulting problems.

The sensor 232 reads the consistency of the output, primarily the sizeof the particles. The programmable logic controller (PLC) in themicroprocessor responds thereto by adjusting the variable speed drivesignals (VSD) sent to pumps 210, 212 and to turbine 202, which bringsthe system into a finely tuned operation.

The internal construction of the manifold 200 is shown in FIGS. 12-15.

In greater detail, FIGS. 12-15 are schematic or graphic presentationsshowing how the holes are drilled into metal block 200 in order to formthe manifold. When viewed from the outside, the metal block 200 appearsas having solid sides with only the entrances of the various holesvisible. The phantom lines shown within rectangles in FIGS. 12-15schematically indicate the paths formed by the bores inside the block.

The output of ASA pump 210 is connected to inlet port 242 which is theentrance to a relatively large diameter bore 300 that terminates at itsbottom in a bulkhead containing a relatively small diameter hole filledby a plug 302 which has an orifice formed therein. In order to adapt thesystem to different processing materials and techniques, ASA,surfactants, etc. the plug 302 may be replaced by another plug having adifferent orifice size.

Any suitable starch/polymer may be inserted into the block 200 via inletport 248 which communicates with bores 306, 308. Again, a small diameterhole is formed at 310 in the bottom of this bore 306 extending from port302 contains a plug 304 with a mixture of starch/polymer.

Water is introduced at inlet port 250. A flow control orifice is housedinside of this bore. The ASA, starch/polymer, and water meet at mixingchamber 316. Bore 308 is closed by plugs 312 and 314.

Depending upon the needs of the system, static mixers (FIGS. 3 and 4)may be inserted into either or both of the bores 306 and 310. Then, theend of either of the bores may be closed by plugs, as may be required byspecific system needs. For example, the transverse bore 308 is hereshown as being plugged at port 312 and bore 310 is shown as beingplugged 314. In other embodiments, the plugs may be removed and suitableconnections may be made to insert a fluid into these holes.

After the ASA, water, and polymer meet and mix in a central mixingchamber 316, closed by plug 317 the resulting mixture is discharged fromthe mixing chamber at output port 203, to the inlet of the turbine pump.

The system bleeds off some portion of the emulsion of ASA and starch asa discharge from turbine 264 and another portion is recirculated via aloop shown by the dot-dashed line in FIG. 11. The recycled emulsionreenters manifold 200 via holes 268 and 270 (FIG. 14). This resultingmixture is an emulsion which is discharged from the mixing chamber atoutput port 272 as the output product of the system.

Any of the various bores which are not used may also be capped by aplug, some plugs having a suitable meter associated therewith. Forexample, a pressure gauge 238, 240 (FIG. 11) may be associated withplugs closing port 318 and 240.

It should now be apparent that most of the pipes used in prior systemshave been eliminated and that short bores inside the mixing manifoldblock 200 have been substituted therefore. Since the adverse effectsresulting from a hydrolyzed ASA build-up varies directly with the areaof the inside surfaces of passage ways carrying the ASA, the inventionsharply reduces the problems growing out of the ASA build-up.

FIG. 16 shows manifold 200 and some of the inputs thereto. At least themanifold 200, and perhaps other equipment, is enclosed in a temperaturecontrolled enclosure 400, such as a cooling housing. This enclosure willkeep the enclosed parts of the system cool to avoid a possiblehydrolyzing of the ASA which occurs when enough heat builds up in theprocessed fluid. This cooling is especially relevant when hot cookedstarch is used as the emulsifier.

Normally, it is enough to merely place the manifold in a temperaturecontrolled enclosure 400. However, it is also within the scope of theinvention to so incorporate any or all other system components in theenclosure. Also, while the temperature controlled enclosure is heresuggested as a cooling housing, it is within the scope of the inventionto provide any temperature controlled enclosure which provides anysuitable temperature profile during the ASA processing. In general,regardless of the temperature or temperature profile that is selected,the principle is to prevent a hydrolyzation or other loss ordeterioration of the ASA.

FIG. 17 broadly shows another approach to heat control in the inventiveASA processing system. Here shown is essentially the same part of thesystem that is shown in FIG. 16. However, instead of a temperaturecontrolled enclosure, a heat exchanger 402 is included in the feed backloop (dot-dashed line 266 ) from pressure controller 222 to recycleimport 270 on manifold 200. The heat exchanger 402 may take any of manydifferent forms such as a plate and frame heat exchanger, a tube heatexchanger, a heat sink having cooling fins, a radiator, a combinationthereof, or another suitable device.

Again, the purpose of the heat exchanger is to maintain a temperatureprofile which will prevent hydrolyzation or another deterioration of theASA. The heat exchanger may also be used in combination with otherdevices, such as the temperature controlled enclosure 400 of FIG. 16, inorder to control the temperature of the input streams of ASA, water, oremulsifier.

FIGS. 18 and 19 are substantially the same, but modified, system that isalso shown in FIG. 11. Therefore, the same reference numerals areretained in these figures for corresponding parts. The description ofthese parts will not be repeated here.

The object of the modified system shown in FIG. 18 is (1) to prevent orreduce the chances of hydrolyzation or other damage to ASA when there isa high temperature either caused by the energy imparted by the turbineor caused by a use of hot cooked starch, and (2) to insure accuracy inthe delivery of processed ASA to a paper machine under changing backpressure conditions.

It should be noted that the input emulsion material at valve 214 is hotcooked starch which will be at a temperature specified by the paper millas part of its proprietary process. Usually, the temperature will besome temperature around 160° F. Therefore, if no cooling is providedeither the subsequently processed ASA particles might be relativelylarge or possibly it might be hydrolyzed. If the ASA particles are toolarge, or are hydrolyzed, they will not interact satisfactorily withmost paper fibers.

The FIG. 18 system modification to the FIG. 11 system includes areplacement of manual direct view flow meters 252, 254 (FIG. 1) withmore accurate analog flow meters 410, 412, which may be connected toaccurately report the input flow of starch at 214 to the main controlpanel 234. Since cooked starch is used, it will have only about 4%solids and, therefore, will not require water dilution. Responsivethereto, the PLC microprocessor controls the valve 426 in the secondaryflow circuit. The cooked starch input valve 224 is self-controlling.

A heat exchanger 414 uses cold water which is externally supplied at416, 418 in order to cool the processed fluid in the recycle loop 266,shown as a dot-dashed line. The cold water is circulated through a coil420 associated with cooling and cooled lines 422, 424. As a result ofthis cooling, the ASA may be reduced to ultrafine particles without anundue heat build-up that might otherwise cause heat damage or a rapidhydrolyzation. This cooling is particularly important when hot cookedstarch is provided at inlet valve 214.

With the modification shown in FIG. 18, there is no need for the valve220 (FIG. 11) leading to the secondary flow line; therefore, it has beeneliminated. The hole in manifold 200 which had been connected to theoutlet pipe at 272 is simply plugged. The out flow from valve 222 issent from turbine 264 directly through valve 222 to the secondary legand the Epic sensor 232 to the output 258.

The recycle stream 266 (shown by a dot-dashed line) is taken directlyfrom the turbine 264 and before passing through valve 222, which maycreate a back pressure applied to the recycle loop. A PLC controlledvalve 426 is provided to control the primary flow rate in the recycleloop.

The advantages of the various modification disclosed in FIG. 18 shouldnow be clear. The inventive system may be connected directly to anautomatic in-line paper making machine. The emulsifier feed stream maybe either a hot cooked starch polymer, or a starch/polymer combination.The programmable logic controller of a microprocessor 236 controlsautomatic valves at check points to insure an accurate delivery ofprocessed ASA despite changing conditions which may occur in theinflowing starch and particularly changing back pressure conditions inthe process line.

FIG. 19 shows another modification of the system of FIG. 11 which isdesigned to reduce cost by eliminating some of the more expensivecontrol valves.

The modification of FIG. 11 that is shown in FIG. 19 included aproportional integral derivative (“PID”) control 430, which is describedin U.S. Pat. No. 5,730,937. The PID controller 430 maintains the flowrates in both the primary and secondary streams. The modification ofFIG. 19 includes the use of analog flow meters 410, 412, as shown inFIG. 18. These flow meters report the incoming flow rates to theprogrammable logic control circuit 236.

The main control panel receives and responds to these reports and to thesignals from the various sensors by sending control signals to avariable speed water pump 432 which increases or decreases the amount ofwater being delivered to the system. This controls the amount ofdilution water supplied to input 250 of the manifold 200 and to thesystem output 258 via check valve 256. With this control over the waterpump 432, it is possible to greatly reduce the precision of control atmany other points in the system and, therefore, the cost thereof,especially the cost of expensive automatic control valves.

Those who are skilled in the art will readily preview how to modify theinvention. Therefore, the appended claims are to be construed to coverall equivalent structure which fall within the true scope and spirit ofthe invention.

1. An apparatus for preparing a sizing emulsion, comprising: a mixing chamber for combining a sizing agent and an emulsifier; a mixing head in said mixing chamber for imparting an energy factor to said sizing agent and said emulsifier to form an emulsion, said energy factor being greater than 361; a recycling loop for recycling a first part of said emulsion in said mixing chamber; and an outlet for outputting a second part of said emulsion.
 2. The apparatus of claim 1, wherein said mixing chamber is a manifold formed of a solid block having at least one bore for conveying said sizing agent, said emulsifier and said emulsion.
 3. The apparatus of claim 1, wherein said mixing head imparts an energy factor of at least about
 620. 4. The apparatus of claim 3, wherein said energy factor is in a range of about 620 to about
 1020. 5. The apparatus of claim 1, wherein said mixing head is a bladed turbine having a speed greater than 3600 rpm.
 6. The apparatus of claim 5, wherein said bladed turbine has a speed of at least about 5,800 rpm.
 7. The apparatus of claim 6, wherein said turbine has a speed in a range of about 5,800 rpm to about 33,000 rpm.
 8. The apparatus of claim 1, wherein said mixing head is a bladed turbine having a blade tip velocity greater than 3,611 ft/min.
 9. The apparatus of claim 8, wherein said mixing head is a bladed turbine having a blade tip velocity of at least about 5,000 ft/min.
 10. The apparatus of claim 1, wherein said mixing head is a bladed turbine having a variable speed drive.
 11. The apparatus of claim 10, further comprising a microprocessor for controlling said variable speed drive to adjust the speed of said multi-blade rotor in response to the particle size of said emulsion.
 12. The apparatus of claim 1, wherein said energy factor is calculated based on a contact time of 1 minute.
 13. An apparatus for preparing a sizing emulsion, comprising: a mixing chamber for combining a sizing agent and an emulsifier; a multi-blade rotor in said mixing chamber for imparting an energy factor to said sizing agent and said emulsifier to form an emulsion, said energy factor being greater than 361 when calculated based on a contact time of 1 minute; a recycling loop for recycling a first part of said emulsion in said mixing chamber; and an outlet for outputting a second part of said emulsion as a finished sizing emulsion.
 14. The apparatus of claim 13, wherein said mixing chamber is a manifold formed of a solid block having at least one bore for conveying said sizing agent, said emulsifier and said emulsion.
 15. The apparatus of claim 13, wherein said multi-blade rotor has a speed greater than 3600 rpm.
 16. The apparatus of claim 15, wherein said multi-blade rotor has a speed of at least about 5,800 rpm.
 17. The apparatus of claim 16, wherein said multi-blade rotor has a speed of about 5,800 rpm to about 33,000 rpm.
 18. The apparatus of claim 13, wherein said multi-blade rotor has a variable speed drive.
 19. The apparatus of claim 18, further comprising a microprocessor for controlling said variable speed drive to adjust the speed of said multi-blade rotor in response to the particle size of said emulsion.
 20. A method of preparing a sizing emulsion, comprising the steps of: (a) combining a sizing agent and an emulsifier to from a mixture; (b) applying a shear force to said mixture to form an emulsion, said shear force having an energy factor greater than 361; (c) diving said emulsion into first and second parts; (d) recycling said first part of said emulsion to rejoin said mixture of step (a); and (e) directing said second part of said emulsion to an output.
 21. The method of claim 20, wherein said sizing agent and said emulsifier are combine in step (a) by injecting said sizing agent and said emulsifier into a manifold formed of a solid block having at least one bore for conveying said sizing agent, said emulsifier and said emulsion.
 22. The method of claim 20, wherein said energy factor of step (b) is at least about
 620. 23. The method of claim 22, wherein said energy factor is in a range of about 620 to about
 1020. 24. The method of claim 20, wherein said shear force of step (b) is applied by a bladed turbine having a speed greater than 3600 rpm.
 25. The method of claim 24, wherein said bladed turbine has a speed of at least about 5,800 rpm.
 26. The method of claim 25, wherein said bladed turbine has a speed in a range of about 5,800 rpm to about 33,000 rpm.
 27. The method of claim 20, wherein said shear force of step (b) is applied by a bladed turbine having a blade tip velocity greater than 3,611 ft/min.
 28. The method of claim 27, wherein said bladed turbine has a blade tip velocity of at least about 5,000 ft/min.
 29. The method of claim 20, wherein said energy factor of step (b) is calculated based on a contact time of 1 minute.
 30. The method of claim 20, wherein said shear force of step (b) is applied by a bladed turbine having a variable speed drive, and further comprising the step of adjusting the speed of said bladed turbine to form an emulsion having particles with a mean diameter in a range of about 0.1 to about 3.0 microns.
 31. The method of claim 30, wherein said emulsion has particles with a mean diameter in a range of about 0.5 microns to about 1.5 microns. 